// Definition for a binary tree node.
function TreeNode(val, left, right) {
  this.val = (val === undefined ? 0 : val)
  this.left = (left === undefined ? null : left)
  this.right = (right === undefined ? null : right)
}

function createTree(arr) {
  if (arr.length < 1)
    return null;
  let NodeArr = [];
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] == null) {
      NodeArr.push(null);
      continue;
    }
    let tempNode = new TreeNode(arr[i], null, null);
    NodeArr.push(tempNode);
  }
  for (let i = 0; i < arr.length; i++) {
    if (NodeArr[i] == null) continue;
    if (2 * i + 1 < arr.length)
      NodeArr[i].left = NodeArr[2 * i + 1];
    if (2 * i + 2 < arr.length)
      NodeArr[i].right = NodeArr[2 * i + 2];
  }
  return NodeArr[0];
}

// function preShow(node) {
//   if (node == null)
//     return;
//   console.log(node.val);
//   preShow(node.left);
//   preShow(node.right);
// }

/**
 * @param {TreeNode} root
 * @return {number}
 */
var maxPathSum = function (root) {
  root = createTree(root);
  if(root.left == null && root.right == null) return root.val;
  let result = -1001;
  function dfs(node) {
    if(node === null) return 0;
    let left = Math.max(0, dfs(node.left));
    let right = Math.max(0, dfs(node.right));
    result = Math.max(result, left + right + node.val);
    return Math.max(left, right) + node.val;
  }
  dfs(root);
  return result;
};
let root = [1,2,3];
console.log(maxPathSum(root));
root = [-10,9,20,null,null,15,7];
console.log(maxPathSum(root));
root = [-3];
console.log(maxPathSum(root));
root = [2,-1];
console.log(maxPathSum(root));
